In the field of mobile communications, it is known to provide a network architecture that is schematically shown in FIG. 1a. A mobile communication network may be divided into a communication control part 1 and an access part 2. The communication control part 1 is arranged to manage call communications to and from mobile communication devices, such as the schematically indicated mobile telephone 3. The access part 2 is arranged to manage the access of mobile communication devices to the communication control part 1. As an example, in mobile communication networks operating according to the global system of mobile communication (GSM), the communication control part 1 is referred to as the network and switching sub-system (NSS), and the access part 2 is referred to as the base station sub-system (BSS). Generally, the access part 2 may also be called an access network, and the communication control part 1 may be called a control network.
The communication control part 1 comprises a plurality of communication control entities, which are referred to as 121-125 in FIG. 1a. Furthermore, the access part 2 comprises a plurality of access control entities referred to as 111-118. Each access control entity 111-118 is respectively associated with a service realm 101-108. A service realm is a physical and/or logical area in which service is provided to mobile communication devices. As such, a service realm can be a location area (LA), a cell, a routing area (RA) or anything similar. As an example, in a GSM network, the network control entities 121-125 can be mobile switching centers (MSC), and the access control entities 111-118 can be base station controllers (BSC). In the context of a mobile communication network e.g. operating in accordance with the general packet radio service (GPRS), the communication control entities 121-125 can be GPRS service nodes (GSN) and the access control entities 111-118 can be radio network controllers (RNC).
It may be remarked that the term “entity” as used in the present specification and claims describes a logical unit for fulfilling a given function, where said logical unit may be present in a single physical unit (such as a network server) or spread out over several physical locations, and may consist of hardware, software or any suitable combination of hardware and software.
In the general architecture shown in FIG. 1a, each of the access control entities 111-118 is connected to one or more communication control entities 121-125. Thereby, each communication control entity 121-125 is enabled to communicate with mobile communication devices in the service realm of a connected access control entity 111-118.
In the example of FIG. 1a, the mobile telephone 3 is in service realm 101, which belongs to access control entity 111, which in turn is connected e.g. with communication control entity 121 via connection 130. In this way, the access control entity 111 lets the mobile telephone 3 access the communication control part 1, more specifically the communication control entity 121, which in turn can fulfil its functions of controlling the establishment, maintenance and termination of communications originating at the mobile telephone 3 and/or directed towards the mobile telephone 3.
It is furthermore known to arrange a mobile communication network of the type shown in FIG. 1a in such a way that the communication control part 1 is arranged to perform a control process such that during the duration of a call communication to a given mobile communication device, one primary communication control entity stays in control of said call communication and communicates with a mobile communication device of which a call communication is being controlled either via an access control entity connected to the primary communication control entity, or via a secondary communication control entity and an access control entity connected to the secondary communication control entity. In this way the secondary communication control entity acts as a relay between the mobile communication device being controlled and the primary communication control.
This will briefly be explained by comparing FIGS. 1a and 1b. In FIG. 1a, a situation is assumed in which the call communication by mobile telephone 3 is being controlled by communication control entity 121. Communication control entity 121 acts as a primary communication control entity. As an example, the system can be arranged in such a way that the first communication control entity that handles the establishment of a call communication from or to a mobile communication device is selected as the primary communication control entity for the entire duration of the call communication being established. Naturally, other methods of selecting a primary communication control entity are possible.
FIG. 1b shows an example where mobile telephone 3 has moved to service realm 106, which is associated with access control entity 116. Access control entity 116 is connected to communication control entity 124 via a connection 131 provided by the control part 1. However, due to the fact that communication control entity 121 is the primary communication control entity, it still performs the call control, and uses communication control entity 124 as a relay to the mobile communication device in service realm 106. A control mechanism of this type is e.g. known from GSM, in which case the primary communication control entity 121 is referred to as an anchor MSC, and the secondary communication control entity 124 is referred to as a relay MSC.
In order to allow for the mobility of mobile communication devices between different service realms, the communication control part 1 is arranged to be able to conduct a so-called handover procedure between different communication control entities. During an ongoing call communication, the primary call control entity (121 in the above-mentioned example) also controls the handover from one secondary communication control entity to another.
For example, if the mobile telephone 3 shown in FIG. 1b moves from service realm 106 towards service realm 107, a given handover triggering process will be started once it is determined that service should be provided by service realm 107 in place of service realm 106. In this event, a request will be sent to the primary communication control entity 121 from the secondary communication control entity 124 or the corresponding mobile communication device in service realm 106, where said request identifies the new communication control entity 125 as a destination. Subsequently, the primary communication control entity 121 establishes a communication with the new secondary communication control entity 125, in order to then use this new secondary communication control entity as a relay towards the communication device in service realm 107.
It is furthermore known to arrange a communication network having the architecture shown in FIGS. 1a and 1b in such a way that certain access control entities are grouped together, and certain communication control entities are pooled together, where the group of access control entities and the pool of communication control entities are associated in such a way that each communication control entity in the pool can communicate with each access control entity in the group. This is shown in FIGS. 1a and 1b, where reference numeral 12 refers to a pool of communication control entities 121-123, and reference numeral 11 refers to a group of access control entities 111-115. As indicated in FIGS. 1a and 1b, a connection mechanism 130 is provided, such that each of the communication control entities 121-123 of pool 12 can communicate with each access control entity 111-115 of group 11. The purpose of such pools and groups is to allow that as long as a mobile communication device moves among the service realms 101-105 associated with the access control entities 111-115 of group 11, no handover procedure is conducted between any of the communication control entities of the pool 12. Such pools and groups are e.g. known in the control of service realms having a high traffic load but small, physical extension, such as micro-cells in metropolitan areas.